Came out to perform preventative maintenance on furnace. Discussed with customer about maintenance being done, and if filters needed changed. Customer stated that she would change them if I just supplied them. Gave customer filters that were needed. Went up into attic and began inspecting the blower assembly, motor, capacitor, electrical components, heating components, heat exchangers and coil condition. Cleaned flame sensor and inducer port. Made sure heat drains were clear of any build up or blockages. Cycled system on and checked amps, temperatures and gas pressure. System is still short on return air, but customer isn’t interested in correcting it at this point. Other than that the system is operating normally at this time.